Hewlett-Packard considered planting moles posing as office workers in two organisations as part of its inquiry into boardroom leaks, new reports suggest.

Details of the extent to which the computer firm was prepared to go to find the source of conversations within its board emerged as the New York Times reported yesterday that HP looked into placing investigators pretending to be secretaries or cleaners in the San Francisco offices of the Wall Street Journal and the technology website CNET, which both carried stories on the company's boardroom discussions.

The newspaper quotes from a memo sent by a senior HP manager that said: "Feasibility studies are in progress for undercover operations (clerical) in CNET and WSJ offices in SF bureaus." It is not known whether any such plans were ever instigated. Another section, referring to "Covert Operations", discussed infiltrating investigators into offices as cleaners. The decision to snoop on people as part of the leak inquiry in 2005 and 2006 has thrown HP into disarray. Patricia Dunn, its chairman, said last week that she would step down in January, apologising for "certain inappropriate techniques" that were used. She said the inquiry was carried out by "third parties" who used methods that "went beyond what we understood them to be". She will remain on the board.

HP admits obtaining phone records of several people, including its own directors and staff, as well as nine journalists from different media outlets. A ruse known as "pretexting" was used in which investigators hired by HP pretended to be their targets, quoting social security numbers to extract personal records from telephone companies. Reports also claim that investigators tried to install software on a computer to monitor a journalist.

Two CNET reporters were told by government investigators that their phone records were seen by HP even before they had written stories about the firm's board.

The San Jose Mercury reported that records were even obtained for Carly Fiorina, the firm's former chief executive who initiated the first leak inquiry in 2005. She was fired that year and is now writing a keenly awaited book about the furore.

The US Congress is looking to see whether HP broke the law. It intends to call Ms Dunn and other HP executives to hearings in Washington next week. Further scrutiny by the department for justice and the securities and exchange commission is likely to follow.